Automatic control of radio transmitters and the like



March 28, 1950 v. H. VOGEL AUTOMATIC CONTROL OF RADIO TRANSMITTERS AND THE LIKE 3 Sheets-Sheet 1 Filed Sept. 11. 1946 INVENTOR VERA/0A! 16. V0 6L ATTORNZY March 28, 1950 v. H. VOGEL' AUTOMATIC CONTROL OF RADIO TRANSMITTERSAND THE LIKE Filed Sept. 11, 1946 L; l l

l I I I VERA/0A! V0654 INVENTOR y ATTORN March 28, 1950 v. H. VOGEL 2,502,396

AUTOMATIC CONTROL OF RADIO TRANSMITTERS AND THE LIKE Filed Sept. 11. 1946 :5 Sheets-Sheet s PfSO/VA/V'i l l l J. 3.3. I I l l I l l I l I l I l Patented Mar. 28, 1950 AUTOMATIC CONTROL OF RADIO TRANS- MITTERS AND THE LIKE Vernon H. Vo'gel, Cedar Rapids, Iowa, assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Application September 11, 1946, Serial No. 696,188

This invention relates to automatically-controlled transmitters and more especially to automatic tuning and antenna loading arrangements therefor.

A principal object of the invention is to provide an improved automatic control system for tuning the amplifier and antenna circuits of a radio transmitter, and for adjusting the loading of the final amplifier.

Another object is to provide an automatic adiusting system for the final amplifier stage of a radio transmitter or the like, wherein a number Oiseparate tuning adjustments are sequentially and automatically effected under control of a common phase discriminator device.

Another principal object is to provide a motor driven tuning control in conjunction with a phase-sensitive discriminator and novel automatic control circuits, whereby false operation of the controls which might arise during the unused rotational arc of the tuning condensers, is avoided.

A feature of the invention relates to a special form of phase discriminator and automatic stepping switch in conjunction with a series of driving motors for the several adjustments of a radio set, whereby the discriminator is connected successively to said motors to determine the direc- V tion.and extent of rotation.

Another feature relates to a plural motor adjusting system for radio sets, whereby successive adjustments of the set are efiected under control of I the resonant conditions in the set, together with a test discriminator of the phase comparison type which is provided with a special checking arrangement, so that if the comparison voltage is -insufficient to control the tuning motor, the motor automatically continues its rotation until brought within the resonant range of the associated part of the set.

Another feature relates to improvements in automatic tuning arrangements responsive to resonance conditions in a radio set, whereby the tuning motor is controlled by the resonance voltage, and also is controlled separately by a voltage which is independent of the resonance voltage. As a result of this feature, the automatic tuning arrangement operates satisfactorily even though such devices as tuning condensers of the 360 rotational type are employed, which are effective for tuning during one-half or less of their complete rotation.

Another feature relates to a novel organization of electron tubes and motor control circuits, with improved checking and interlocking arrange- 16 Claims. (01. 250 -17) ments for insuring accuracy and reliability in the automatic tuning and loading of the final amplifier stage of a radio transmitter and the like.

A still further feature relates to the novel organization, arrangement and relative interconnection of parts which cooperate to provide an improved motor control arrangement for the automatic adjustment of radio sets and the like.

Other features and advantages not specifically enumerated will become apparent after a con-' sideration of the following detailed descriptions and the appended claims.

In the drawing,

Fig. 1 is a schematic wiring diagram of a radio transmitter system and a portion of the automatic tuning and loading controls according to the invention. 7

Fig. 2 is a schematic wiring diagram of the remaining portions of the automatic tuning and loading controls of Fig. 1.

Figs. 3 and 4 respectively are graphs explana tory of the operation of Figs, 1 and 2.

While the invention will be described as embodied in a radio signalling system, it will be understood that the inventive concept is equally well applicable to other systems such as high,

frequency induction heating systems, or any similar system which requires automatic tuning of an amplifier to resonance and automatic loading of the output stage.

Referring to Fig. 1, there is schematically represented by the block l0, any well-known high frequency or radio frequency generator such for example as the usual adjustable frequency carrier generator, and if necessary, the usual frequency multipliers and amplifier stages of a radio trans-' variocoupler 20, whose primary winding 2| isv tuned by variable condenser 22. The secondary winding 23 is connected in the antenna circuit which likewise can be tuned by the series condenser 24. Either or both of the windings of the variocoupler Zllmay be rotatable to effect differ- 3 ent coupling ratios between the amplifier and the antenna circuit.

Associated respectively with the condensers i6, 22, 24, and with the rotatable coil of the variocoupler 2B, are the driving motors 25-28 (Fig. 2). Each motor may be of the automatic controlled shaded pole type, comprising main field windings 29--32, and respective pairs of shaded pole windings 3334, 353i5, 3l38, 394 l. These motors are designed so that the direction of rotation is determined by which one of the shaded pole windings is short-circuited. The relative direction of rotation under control of the shaded pole windings is indicated schematically by the respective curved arrows. When both shaded pole-windings of a given motor are short-circuited, that motor is quickly stopped and held. in stopped-position.

For the purpose of controlling the selective short-circuiting of the directional control windings of the motors, there is provided a phase discriminator 29, comprising a pair of tetrodes 30, 3|, which are successively effective so as to compare the resonance conditions at the input of amplifier M; at the output of amplifier i4; and at the antenna circuit. The motor 2! which tunes the variocoupler is controlled by a sensi tive meter-type relay 4| which is connected in series with the high frequency choke coil 42. in the D. C. plate supply circuit of tube !4. The principle of quadrature relationship of voltages between coupled parallel-resonance circuits is utilized to control the discriminator 29.

In order to control the sequential operation of motors 25, 28, and 28, there is provided a stepping switch 43, comprising rotatable brushes 44-48, gan' ed together on a common shaft for unitary movement as represented by the dotted line connections. This common shaft has attached thereto the usual ratchet wheel (not shown) or similar step-by-step device which is actuated by a pawl (not shown) under control of the stepping magnet 49, so as to advance the brushes in a step-by-step manner. Each brush is associated with a set of three fixed contacts which are interconnected with the various motor windings as shown. To insure the proper timing in the stepping of the switch brushes, thereis provided a special time relay tube 58. which in turn is controlled by a relay 5| responding to the difference in plate currents through discriminator tubes 3D, 3!.

The condensers I5, 22 and 24 are all of the 360 rotational type, that is to say when the rotor plates are fully meshed with the stator platesthe condensers are at full capacity and as the rotor cuit, it is necessary to block out the discriminator action during one of these 180 port ons. For this purpose, respective limit switches 54, 55' and 5B are provided for the respective condensers. These limit switches prevent operation of thediscriminator during the unused 180 rotation of the respective condenser rotors by opening the common.

cathode return circuit of tubes 30, 3!. In order to, make sure that the rotor plates are always brought into the resonating portion of the condenser rotation so that the discriminator is always within its control region as indicated in Fig. 4, there is provided a grid-controlled Thyratron tube 52 which controls a relay 53. The arrangement is such that this discriminator control is assured so that the tuning motors for each condenser rotates in a clockwise direction unless the tuning condenser is already within the discriminator control range. When the rotor plates are out. of. this discriminator control range, the tube 52 is not plate conductive and the relay 53 is deenergized. As a result, a D. C. voltage, for example +27 volts, is applied in such a way as to cause the particular motor which is in circuit (dependent upon the position of switch it) to continue rotating clockwise so as to bring the rotor plates'into proper discriminator control range with the stator plates. When the condenser reaches discriminator control range, the cathode load voltage of tubes 30, Si, rises as shown in Fig. 4, causing Thyratron 52 to become conductive and thus causing operation of relay 53. Operation of relay 53 as will be described hereinbelow, connects the test relay 5i in circuit,

and relay 5! maintains its contacts closed as long as there is suficient difference of potential across the respective plate load-resistors of tubes 38 and 3i.

Assuming that the device Ill and condenser i2 have been adjusted to a new frequency setting, the manually operable button 5? is momentarily operated, closing a direct circuit from the +27 volt terminal through the Winding of stepping switch magnet 49, causing the switch to return to normal position, wherein thebrushes are all in contact with the #1 contacts of their associated sets, this position being shown in Fig. 2 of the drawing. It will be noted that when the stepping switch is in position #1, a circuit is completed from ground through brush 45 and its #1 contact over conductor 58 through the winding of relay 59. Relay 59 operates, and the control grids Bil and iii are connected together and through the armature 62 and front contact 63 to the input inductance 15 of tube 14. If the input-circuit-of tube Ml isin resonancewiththe,

output circuit of device H], the phase shift tween these two circuits will be very close to Sincethe plates of bothtubes 3D and Bi are connected to opposite phased, sides of the induce.

the respective plate resistors 88,10, are equaL.

Under these conditions, a voltage willbe developed across the common cathode resistor ll which is applied to the control grid E2 or". the Thyratron tube 52, causing it to be plate current conductive and completing a circuit traceable from the plus D. C. terminal 13, armature l4 and back contact E5 of relay 1B, conductor 11, winding of' relay 53, plate-to-cathode of tube. 52 to ground. Relay 53 operates and connects the nongrounded terminals oi the resistors 69, 1E}, across the.

winding of relay 5!. Since the Voltages developed across resistors 59, 'Hl, are equal in the abovedescribed resonance condition, relay 5| remains deenergized. However,- equal currents flow through the rectifier-s l8 and 19 and thence through respective relay; windings 80, 8}, which.

thereupon operate their-associated contact sets. Thus, ground at point 82 is connected through armature 83 and contact 84 to conductor 85, switch arm 44 and contact 86 to the-winding 33 of motor 25. Similarly ground is connected through armature 8! and contact 88 to conductor 89, Switch arm 45, contact 98 to winding 34. Thus motor 25 remains at rest.

Since relay did not operate, the negative 45 volt battery at terminal 9I is disconnected from conductor 92, and plate current is permitted to flow through the tube 58 and thence through the winding of relay I6. As a result, ground at point 93 is connected through armature 94, contact 95, switch arm 48, contact 96, through the winding of stepping relay 49 to battery. As a result, the switch arms 44-48 are advanced to their #2 contacts. As a result of this, the ground at switch arm 46 is disconnected from conductor 58, resulting in the release of relay 59. brushes 41 and 48 continue to ground their respective #2 contacts. It should be noted that in positions #1 and #2 of switch arm 41, ground is extended through the normally closed contacts 91 of the limit switch which is controlled by motor 28. Therefore, winding 39 is short-circuited causing the motor 28 to rotate in a clockwise direction until the variocoupler 28 arrives at minimum antenna coupling whereupon the switch 91 is opened. The phase shift of the amplifier I4 is 180 so that the quadrature re1ationship between the tuned combination I5, I6,

and the output circuit of amplifier I4 at resonance, is not destroyed. I

Upon the release of relay 59 as above described, control grids 68, 6|, of the discriminator are connected through armature 62 and contact 98 to the output circuit of the amplifier I4. Relay 59 However, the

at its armature 99 and contact I88 also applies a reduced screen grid voltage from the +500 volt terminal I8I, resistance I82, conductor I83, to the screen grid I84, to facilitate resonating of the plate circuit of amplifier I4. If the plate circuit of amplifier I4 is at resonance, equal voltages will appear across relay 5i as above described, resulting in the grounding of both windings 35 and 36 of motor 26, whereupon relay I6 operates, as above described, and causes the stepping magnet 49.to move the switch arms 4448 to position #3. In this position, a circuit is closed from the +27 volt terminal I85 through the winding of relay I86, switch contact I8! and switch arm 4'! to ground. Relay I86 at its armature I81 and contact I88 short-circuits resistance I82, thus applying normal full screen voltage to the screen grid I64. the proper position for resonating the antenna circuit at the desired frequency, equal voltages appear across relay 5| as above described, resulting in the operation of relays 88 and 81, and the short-circuiting of windings 31 and 38 of motor 21 which therefore remains at rest. In this #3 position of the stepping switch, the negative bias battery I89 is connected between the control grid H8, switch contact III and switch arm 46 to ground. The application of this negative bias battery prevents operation of relay I6, permitting the discriminator and control circuits to retain control of motor 21 after the antenna resonating operation is completed. Furthermore in position #3, the operating circuit for the stepping magnet 49 is broken at contact H2, thus preventing further stepping motion of the switch except as desired by the manually operable switch 51 as above described, In position #3, the short- If the condenser 24 is in circuit-for the left-hand winding 39 of motor 28 is removed and the winding 48 is short-circuited through the contact H3, and armature I I4 of the meter type relay M and thence through the contact H5 and armature II6 of the previously operated relay I86. Motor 28 therefore begins to rotate so as to increase the coupling of the variocoupler 23. As this coupling increases, the plate current drawn by tube I4 also increases and introduces reactive components into the plate circuit thereof, which reactance components exist if th antenna circuit under control of condenser 24 is not tuned to resonance at the operating frequency. It should be noted that in position #3 of the stepping switch, the windings of motor 21 are still under control of the relay 5| and the rectified currents through the rectifiers I8 and I9. Since as above assumed the antenna circuit is in resonance, both windings 31 and 38 are shortcircuited and motor 21 stays at rest.

The tuning cycle is thus completed and all motors are at rest. However, any changes which occur in the plate circuit or output of amplifier I4 or in the antenna circuit, which changes tend to destroy the condition of resonance, are automatically compensated for by the discriminator. In other words, the stepping switch remains in position #3 so as to connect the discriminator 29 and meter relay 4I continuously for control of motors 2'! and 28. When it is desired to set the transmitter to a different radiating frequency, the generator I8 and tuning condenser I2 are reset to the new frequency and the manually operated button 5'! is operated which results in the restoration of the stepping switch to its #1 position to repeat the foregoing cycle of operations.

In the foregoing description, it has been assumed that the elements 16, 22, 24 and 28 are all in the proper position for the desired resonance and plate loading. A description will now be given of the operation when all said elements 2528 are ofi resonance and are ofi proper plate loading. With the stepping switch in position #1, let it be assumed that the generator I8 and the condenser I2 have been tuned to a difierent frequency. Under this condition, the phase rela-- tionship between the tuned combination II, I 2, and the tuned combination I5, I6, will not be equal to 90 and the voltage applied to the control grids 68 and 6| will have some angular leading or lagging quadrature relationship, thereby causing unequal voltages to appear across the resistors 69 and '58, depending upon whether the phase relation is leading or lagging. In other words, the voltage developed across said resistors 69 and I8 determines the amount of off resonance of the combination I5, I6, and the direction in which the motor 25 must be turned to restore the proper resonance. However, if the grid circuit of amplifier I4 is very far from resonance, the voltage applied to the grids 68 and 61 may be so small as to develop insuficient voltage across resistors 69 and 78 for control purposes. Referring to Fig. 3, there is shown the graphical relation between the plate D. C. voltage output of the discriminator 29 plotted against capacity of tuning condenser I6 for a given frequency- Fig. 4 is a graph showing a plot of the discriminator cathode currentagainst the same capacity of condenser I 6. From these two graphs, it will be clear that the dis-' criminator control is effective over only approximately one-third of the total tuning range of the condenser l6. It is important therefore, that 7 regardless of thefrequency'setting oil the system, the condenser It should at all times be brought within its effectivev control range. It is for this purpose that the Thyratron type tube 52 is provided; As above. described, it the condenser l6. is so far off resonance as to develop insufficient voltage across the commoncathode resistor H, tube 52 is non plate-current conductive resulting in the deenergization of relay 53 which automati-- cally continues to turn motor 25 in a clockwise directionso as to bring condenser IE into effective resonance range. This is so because with relay 53 d'eenergized, +27 volts is applied through the contacts of relay 53 to the plate of rectifier 19, so only this rectifier causes current to flow through relay 8! which thereupon operates to short-circuit the motor winding 33. When condenser it reaches the beginning of its eiiective resonating range, tube 52 begins to conduct and relay 53 operates, thus transferring the control of windings and 3s to'the respective discriminator resistors 59 and i0. Since it has been assumed that condenser Iii is off resonance, a voltage difieren-ce is applied across relay 5i resulting in its operation and the application of the negative 45" volt battery at terminal to the grid of tube 50, thus preventing operation of relay 16. Furthermore, depending upon the relative magnitudes of the voltages developed at resistors 69 and Hi, the proper one of the relays 8G or 8! will be operated so as-to short-circuit the proper winding 33 or 3 1 of the mot-or 25, resulting in the rotationoi a condenser it to the resonance point. At this point, relay El releases and motor 25 comes to rest. As above described, during the unused 180 rotation of the rotor plates of condenser l6, that is when these plates are not within the effective discriminator control region (as indicated in Fig. 4) the discriminator 29 is effectively removed from the control circuit by its respective limit switch 55.

A short interval after condenser l6 finally reaches the proper resonance position as determined by the time constant of the condenser H1 and resistor H8, the grid i it is restored to sufficient bias to enable the tube 58 to be plate current conductive and resulting in the operation of relay 15. This immediately closes the circuit of stepping magnet as and rotates stepping switch to position #2. In position #2, the motor 26 is brought under control of the discriminator and since a new setting is required, the proper winding or 36 0f motor 26 will be short-circuited so as to rotate the condenser 22 to the resonating point. Here again, if the condenser is too far off resonance at the start, the motor circuit will be maintained closed under control of deenergized relay 53, and when the eiiective resonating range ofthe condenser is reached, relay 53 reoperates and places the windings of motor 26 again under control of the discriminator. Likewise, if the condenser 22 is rotated through itsunused 180, its associated limit switch 55 maintains the common cathode circuit of the discriminator open so as to insure sufficient rotation of the motor 25 to bring thecondenser 22 into its effective resonating range. It should be observed thatin' positions #1 and #2 of the stepping switch, ground is extended through switch arm 46 and the associated first and second contacts and thence through the limit switch 91', to ground the winding 39 of motor 21, thus causing this motor to drive the variocoupler 20' to a position corresponding to minimum antenna coupling, whereupon the switch 9'! opens and the motor stops. Also. duri'ngposition #Zof the switch, a reduced screen grid voltage is applied as above describedto the screen grid 164. When resonance is reached, relay l8releases resulting in the operationof relay is and the stepping of the switch toiposition #3.

Iii-position #3, relay I06 operates to apply the normal screen grid voltage on screen grid I04. The discriminator 29 is now connected so as to control motor 28. Battery I69 also applies negative bias to grid III] to prevent operation of relay 16, thus permitting the stepping switch to stay in position #3. Relay I being operated; the winding 39 is grounded through armature H3; contact H4, contact H5 and armature MB. This therefore results in an increase of the coupling to the antenna circuit. This also increases the plate current drawn by amplifier l iand introduces reactive components into the plate circuit of that amplifier, which reactive components are dependent upon the off resonance of the antenna circuit. At the same time, the discriminator 29 is connected to control the motor 28 which causes the condenser 24 to be tuned to resonance. Since the meter relay 4| is connected directly in the D. C. plate circuit of tube It, when theplate current rises above its rated value, relay 4| operates and short-circuits the winding 40, thus restoring the variocoupler 23 to the proper position corresponding to the rated plate current. In other words, relay 4| continues to increase the coupling between the antenna circuit and amplifier l4, and the discriminator continues to operate motor 28 until the antenna circuit is resonated and coupled to ampl'ifi er l4 and to that amp ifier draws rated plate current at resonance. Thereupon, motors 27 and 28- stop and the complete system is tuned to resonance and proper antenna coupling. The stepping switch stays in its third position so as to provide a cont nuous check on the antenna tuning and upon the degree of antenna coupling through the variocoupler 23. thus providing an automatic control of the loading on the amplifier l4 so as to insure that the tube 14 draws its proper rated plate current at re onance.

Wh e one particular embodiment has been described herein. it will be understood that various' changes and modifications may be made therein, without d parting from the spirit and scope of the invention.

What is claimed is:

1. In a wave tran m ssion svstem, a fir t tuned c rc it, a s cond tu ed circuit. a motor for operating a tuning e ement of said second circuit to brine: it into reson nce with said first circuit said tun ng element being of a type which is ineiiect ve to tune said second circuit to resonance for approximately one-half of its movement, a limit switch operated when said tuned element reaches the limit of its resonating effectiveness, a first motor control c rcuit selectively responsive to a control voltage determined by the condition y of resonance of said second circuit with. respect to said first circuit,,means to develop under control of the relative resonance conditions of the first and second circuits. said motor control voltage with an effective control ma nitude only when said tuning, element is within effectiveresonating. range at a selected frequency, and another motor control circuit controlled by said. limit switch to restore said tuning element automatically to its effective resonating range.

2. A system according to claim 1 in which said other motor control circuit includes a relay which is iefiectiv'e when the first motor control circuit receives insufiicient effective motor control voltage as a result of the off resonance of said second circuit, to render said other motor con trol circuit effective.

3. In a system of the character described, a first tuned section, a second tuned section, a third tuned section, an adjustable coupling between the second and third sections, respective motors for operating the tuning elements of said tuned sections and for adjusting the said coupling, an input device for the first section tuned to a preselected frequency, a network for producing motor control voltages determined by the comparative resonance settings of said input device and said sections successively, a step-by-step selector switch for automatically associating said tuned sections successively for control by said network and said input device, a first tuning motor for said first tuned section, a second tuning motor for said second tuned section, a third tuning motor for said third tuned section, a fourth motor for adjusting said coupling, each of said motors having a pair of directional control windings, said step-by-step switch being a three-position switch having a plurality of contact brushes, the first and second brushes in #1 position associating the windings of said first motor with said network, the third brush in #1 position being connected to a switching relay which associates the first tuned section with said network, the fourth brush in #1 position closing a circuit for only one of the directional windings of said fourth tuning motor to cause said coupling to assume a reference position, a fifth brush effective in #1 position to control the circuit of the stepping magnet of said switch, said first and second brushes in #2 position associating the motor windings of the said second motor in circuit with said network, said third brush in #2 position causing the said second tuned section to be associated with said network, said fourth brush in #2 position continuing the said circuit for the said one winding of said fourth tuning motor, the fifth brush in #2 position continuing the control circuit for said stepping magnet, said first and second brushes in #3 position associating the windings of the said third tuning motor for control by said network, said third brush in #3 position connecting a lock-out circuit for said stepping magnet, and said fifth brush in #3 position opening the circuit-of said stepping magnet.

4. A system according to claim 3 in which, an

amplifier tube is connected between said first and second tuned sections and said fifth brush in #1 and #2 positions is connected in circuit with a switching relay which reduces the potential on one of the electrodes of the amplifier tube, and in #3 position said fifth brush restores the said potential to normal. 5. A system according to claim 3 in which said fifth'brush in #1 and #2 positions connects the said stepping magnet through a time delay device to insure that said stepping switch remains in its set position until completion of the automatic tuning of the respective tuned sections.

6. In a system of the character described, a source of radio frequency waves tuned to a selected frequency, an amplifier tube for said radio frequency waves, said tube having a tunable input circuit and a tunable output circuit, a tunable antenna circuit, an adjustable coupling between said antenna circuit and the output circuit of said tube, a pair of grid-controlled tubes having their plates connected in phase opposition for A. C. excitation across the said source, and their control grids connected in like phase through a switching relay to the said tuned input circuit, a common differential output circuit for said tubes, a test relay connected across said output circuit, a pair of oppositely poled rectifiers also connected across said output circuit, a pair of motor control relays each connected in series with a corresponding one of said rectifiers, a first tuning motor for said tunable input circuit, a second tuning motor for said tunable output circuit, a third tuning motor for said tunable antenna circuit, a fourth tuning motor for said adjustable coupling, each of said motors having a pair of directional control windings, a step-bystep switch for automatically associating the windings of said motors successively with said pair of motor control relays, means automatically advancing said switch successively from a first position to second and third positions as each of said tuned sections is automatically tuned to resonance with said source, means controlled by said test relay for delaying the successive steppin of said switch until the particular tuned section is automatically brought to proper resonance, each of said tunable circuits having a tuning element which is effective to resonate the associated circuit only over a limited portion of its movement, and another motor control circuit which is effective for automatically moving said tuning element into its effective tuning range.

'7. A system according to claim 6 in which said pair of grid-controlled tubes have a common cathode load resistor, a grid-controlled gaseous conduction tube has its control grid connected to said cathode resistor so as normally to be plate current conductive only when a predetermined threshold differential voltage exists at the common output circuit of said tubes, a relay connected to be operated by the plate current of said gaseous tube, said relay when normal applying a conductive bias to only one of said pair of rectifiers to cause the particular motor which is connected in circuit by the stepping switch to rotate in a direction and to an extent sufficient to insure that the tuning element of the associated tuned section is brought within its effective resonating range.

8. In a system of the character described, an input device tuned to a selected frequency, an amplifier tube coupled to said device, said amplifier tube having tuned input and tuned output circuits arranged to be automatically resonated at said se ected frequency, a phase discriminator for controlling the resonating of said circuits, a load circuit adjustably coupled to said output circuit, and means automaticall effective when said tuned circuits are being automatically resonated for automatically reducing said coupling substantially to zero.

9. A system according to claim 8 in which said tube is of the tetrode type and means are automatically provided for reducing the normal voltage D. C. potential on one of the grid electrodes below its normal operating value while said tuned circuits are being automatically resonated.

10. A system according to claim 8 in which said phase discriminator comprises a pair of shield grid tubes having their plates excited in phase opposition by the wave energy from said input device, with the shield grids connected to a steady D. C. potential, and with the control grids connected in like. phase through aswitching re.-

lay-- effective in one position to connect said conrol grids to said tuned input circuit, and effective in another position to connect said control grids in like phase to said tuned output circuit.

11. In a wave transmission system, a first parallel tuned resonant circuit, a second parallel tuned resonant circuit coupled to thefirst circuit, at least one of said circuits having a movable tuning member which effectively resonates said one circuit only during a certain range of movement of said member, a reversible motor for operating said member, a phase discriminator having a pair of grid-controlled tubes with their control grids connected to the second tuned circuit for excitation in like phase, means to excite the plates of said tubes in phase opposition from said first circuit, a plate load device in the plat circuit of each of said tubes and having substantial voltages developed thereacross only when said movable member is in the range of its movement where it effectively resonates said one of said circuits, directional control circuits for said motor respectively controlled by said loaddevices, and means independent of said load devices and operating only when said movable member is in its range of movement where it does not effectively resonate said one of said circuits to close the particular directional control circuit for said motor which is required to bring said member into its effective resonating range of movement.

12. In a wave transmission system a first section to be tuned to resonance, a second section to be tuned to resonance with the first section, each of said sections having a tuning element which is effective to tune the associated section only'during a fraction of the total range of movement of the member, a phase discriminator for comparing the phases of the wave energy in the said two sections to produce a pair of equal control voltages only when both sections are in resonance and to produce diiferential voltages when said sections are out of resonance, a pair of relays each selectively responsive to the mag nitude and sign of said differential voltage, a reversible motor having a pair of dfrectional control windings each controlled respectively by one of said relays, a connection from said motor to a tuning element of one of said sections for controlling its condition of resonance, and circuit connections independent of said control voltages for controlling the proper one or said directional control windings to cause the motor to move the tuning element of said one of said sections into its effective tuning range, said phase discriminator comprising a pair of grid-controlled electron tubes having their plates and control grids eX- cited in phase quadrature by the wave energy in said first section and said second section, a pair of plate load resistors each connected in the plate load circuit of a respective one of said tubes, and a pair of differently polarized rectifiers connected in parallel between the high potential terminals of said load resistors.

13. In a wave transmission system a first section to be tuned to resonance, a second section to be tuned to resonance with the first section, each of said sections having a tuning element which is effective to'tune the associated section only during a fraction of the total range of movement of the member, a phase discriminator for comparing the pha es of the wave energy in thesaid two sections to produce a pair of equal control voltages only when both sections are in resonance and to produce differential voltages when said sections. are out of resonance, a pair of relays each. selectively responsive to the magnitude and sign of said differential voltage, a rever Lisl motor having a pair of directional. control windings eachcontrolled respectively by one or said r lays, a connection from said motor to a tuning element of one of said sections for controlling its condition of resonance, and circuit connections independent of said control voltages for controlling the proper one of said directional control windings to cause the motor to move the tuning element of said one of said sections into its effective tuning range, said discriminator comprising a pair of grid-controlled electron tubes having their plates excited by the wave energy from said first section and their control grids excited in like phase by the wave energy in the said second section, a plate load resistor for each tube; and said pair of relays are connected through a pair of rectifiers differentially to said plate load resistors.

is. In a wave transmission system a first section to be tuned to resonance, a second section to be tuned to resonance with the first section, each of said sections having a tuning element which is effective to tune the associated section only during a fraction of the total range or movement of the member, a phase discriminator for comparing the phases of the wave energy in the said two sections to produce a pair of equal control voltages only when both sections are in resonance and to produce differential voltages when said sections are out of resonance, a pair'of relays each selectively responsive to the magnitude and sign of said differential voltage, a reversible motor having a pair of directional control windings each controlled respectively by one of said relays, a connection from said motor to a tuning element of one of said sections for controlling its condition of resonance, and circuit connections independent of said control voltages for controlling the proper one of said directional control windings to cause the motor to move the tuning element or said one of said sections into its elTective tuning range, said discriminator comprising a pair of grid-controlled electron tubes having their plates and control grids excited by the wave energy in said sections to produce substantial motor control voltages in their respective plate load circuits only when a tuning element of said second section is in effective resonating range, a relay responsive to said control voltage below a pre-determined minimum, a motor for operating said tuning element, a selectively reversible motor circuit controlled by the said control voltage above said minimum, and a motor operating circuit controlled by said relay for insuring that said tuning element is brought into its efifective resonating range so-as to restore control of said selective motor circuit to said control voltage.

15. In a wave transmission system, a first tuned circuit, a second tuned circuit, motor for automatically operating a tuning element of the second circuit to bring it into resonance with said first circuit, a first motor control circuit selectively responsive to the quadrature phase relation between said circuits, means-to develop under control of said phase relation a motor control voltage which has an effective value for motor control purposes only when said tuning element is within its eifective resonating range at a selected frequency, and another motor control circuit effective when said tuning element is out of its said eiiective resonating range for automatically restoring it to said range until the firstmentioned control voltage is of sufficient magnitude effectively to control said first motor control circuit, the first-mentioned motor control circuit including a phase discriminator which de velops a differential motor control voltage in response to the phase quadrature relation between the Wave energy in the first and second circuits, and the second-mentioned motor control circuit includes a grid-controlled gaseous conduction tube which is selectively conductive in response to the magnitude of the resonance voltage of the second circuit.

16. In a wave transmission system, a first tuned circuit, a second tuned circuit, a motor for automatically operating a tuning element of the second circuit to bring it into resonance with said first circuit, a first motor control circuit selectively responsive to the quadrature phase relation between said circuits, means to develop under control of said phase relation a motor control voltage which has an efiective value for motor control purposes only when said tuning element is within its effective resonating range at a selected frequency, and another motor control circuit effective when said tuning element is out of its said effective resonating range for automatically restoring it to said. range until the firstmentioned control voltage is of suflicient magnitude effectively to control said first motor control circuit, the first-mentioned motor control circuit including a phase discriminator which develops a differential motor control voltage in response to the phase quadrature relation between the wave energy in the first and second circuits; 35

and the second-mentioned motor control circuit includes a grid-controlled gaseous conduction tube which is selectively conductive in response to the magnitude of the resonance voltage of the second circuit, a relay which is controlled by the plate-to-cathode current of said gaseous conduction tube, a pair of oppositely poled rectifiers connected in parallel across the output of said discriminator, said relay when operated rendering said rectifiers selectively conductive in accordance with the control voltage developed at the output of said discriminator, said relay effective when released rendering only one of said rectifiers conductive and independently of the output control voltage at said discriminator.

VERNON H. VOGEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,284,612 Green et al May 26, 1942 2,358,454 Goldstine Sept. 19, 1944 2,374,729 Cantelo May 1, 1945 2,376,667 Cunningham et a1. May 22, 1945 2,417,191 Fox Mar. 11, 1947 2,462,856 Ginzton Mar. 1, 1949 2,462,857 Ginzton Mar. 1, 1949 OTHER REFERENCES Auto Resonator Transmitter, Radio magazine, June 1939, pp. 9 to 13, 74 and 75. 

